def app(environ, start_response):
    start_response('200 Ok', [('Content-Type','text/html')])
    file_name = environ['PATH_INFO'][1:] or 'index.html'
    print('file_name', file_name)
    HTML_ROOT_DIR = 'chapter/15/15.2//Views/'
    try:
        file = open(HTML_ROOT_DIR + file_name, 'rb')   
    except IOError:
      response = 'The file is not found!'
    else:
       file_data = file.read()
       file.close()
       response = file_data.decode('utf-8')
    return [response.encode('utf-8')]